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The email package is a library for managing email messages, including
MIME and other RFC 2822-based message documents. It is specifically not
designed to do any sending of email messages to SMTP (RFC 2821), NNTP, or
other servers; those are functions of modules such as smtplib and
nntplib. The email package attempts to be as RFC-compliant as
possible, supporting in addition to RFC 2822, such MIME-related RFCs as
RFC 2045, RFC 2046, RFC 2047, and RFC 2231.

The primary distinguishing feature of the email package is that it splits
the parsing and generating of email messages from the internal object model
representation of email. Applications using the email package deal
primarily with objects; you can add sub-objects to messages, remove sub-objects
from messages, completely re-arrange the contents, etc. There is a separate
parser and a separate generator which handles the transformation from flat text
to the object model, and then back to flat text again. There are also handy
subclasses for some common MIME object types, and a few miscellaneous utilities
that help with such common tasks as extracting and parsing message field values,
creating RFC-compliant dates, etc.

The following sections describe the functionality of the email package.
The ordering follows a progression that should be common in applications: an
email message is read as flat text from a file or other source, the text is
parsed to produce the object structure of the email message, this structure is
manipulated, and finally, the object tree is rendered back into flat text.

It is perfectly feasible to create the object structure out of whole cloth —
i.e. completely from scratch. From there, a similar progression can be taken as
above.

Also included are detailed specifications of all the classes and modules that
the email package provides, the exception classes you might encounter
while using the email package, some auxiliary utilities, and a few
examples. For users of the older mimelib package, or previous versions
of the email package, a section on differences and porting is provided.

This table describes the release history of the email package, corresponding to
the version of Python that the package was released with. For purposes of this
document, when you see a note about change or added versions, these refer to the
Python version the change was made in, not the email package version. This
table also describes the Python compatibility of each version of the package.

email version

distributed with

compatible with

1.x

Python 2.2.0 to Python 2.2.1

no longer supported

2.5

Python 2.2.2+ and Python 2.3

Python 2.1 to 2.5

3.0

Python 2.4 and Python 2.5

Python 2.3 to 2.6

4.0

Python 2.5 to Python 2.7

Python 2.3 to 2.7

5.0

Python 3.0 and Python 3.1

Python 3.0 to 3.2

5.1

Python 3.2

Python 3.2

After Version 5.1 (Python 3.2), the email package no longer has a version that
is separate from the Python version. (See the What’s New in Python documents
for the respective Python versions for details on changes.)

Here are the major differences between email version 5.1 and
version 5.0:

It is once again possible to parse messages containing non-ASCII bytes,
and to reproduce such messages if the data containing the non-ASCII
bytes is not modified.

Given bytes input to the model, get_payload()
will by default decode a message body that has a
Content-Transfer-Encoding of 8bit using the charset
specified in the MIME headers and return the resulting string.

Given bytes input to the model, Generator will
convert message bodies that have a Content-Transfer-Encoding of
8bit to instead have a 7bit Content-Transfer-Encoding.

New class BytesGenerator produces bytes
as output, preserving any unchanged non-ASCII data that was
present in the input used to build the model, including message bodies
with a Content-Transfer-Encoding of 8bit.

Here are the major differences between email version 5.0 and version 4:

All operations are on unicode strings. Text inputs must be strings,
text outputs are strings. Outputs are limited to the ASCII character
set and so can be encoded to ASCII for transmission. Inputs are also
limited to ASCII; this is an acknowledged limitation of email 5.0 and
means it can only be used to parse email that is 7bit clean.

All modules have been renamed according to PEP 8 standards. For example,
the version 3 module email.Message was renamed to email.message in
version 4.

A new subpackage email.mime was added and all the version 3
email.MIME* modules were renamed and situated into the email.mime
subpackage. For example, the version 3 module email.MIMEText was renamed
to email.mime.text.

Note that the version 3 names will continue to work until Python 2.6.

The email.mime.application module was added, which contains the
MIMEApplication class.

Methods that were deprecated in version 3 have been removed. These include
Generator.__call__(), Message.get_type(),
Message.get_main_type(), Message.get_subtype().

Fixes have been added for RFC 2231 support which can change some of the
return types for Message.get_param
and friends. Under some
circumstances, values which used to return a 3-tuple now return simple strings
(specifically, if all extended parameter segments were unencoded, there is no
language and charset designation expected, so the return type is now a simple
string). Also, %-decoding used to be done for both encoded and unencoded
segments; this decoding is now done only for encoded segments.

The FeedParser class was introduced, and the
Parser class was implemented in terms of the
FeedParser. All parsing therefore is
non-strict, and parsing will make a best effort never to raise an exception.
Problems found while parsing messages are stored in the message’s defect
attribute.

All aspects of the API which raised DeprecationWarnings in version 2
have been removed. These include the _encoder argument to the
MIMEText constructor, the
Message.add_payload() method, the Utils.dump_address_pair()
function, and the functions Utils.decode() and Utils.encode().

New DeprecationWarnings have been added to:
Generator.__call__(), Message.get_type(),
Message.get_main_type(), Message.get_subtype(), and the strict
argument to the Parser class. These are expected to
be removed in future versions.

The pickle format for Message instances has changed.
Since this was never (and still isn’t) formally defined, this isn’t
considered a backward incompatibility. However if your application pickles
and unpickles Message instances, be aware that in
email version 2, Message instances now have
private variables _charset and _default_type.

Several methods in the Message class have been
deprecated, or their signatures changed. Also, many new methods have been
added. See the documentation for the Message class
for details. The changes should be completely backward compatible.

The object structure has changed in the face of message/rfc822
content types. In email version 1, such a type would be represented
by a scalar payload, i.e. the container message’s
is_multipart() returned false,
get_payload() was not a list object, but a
single Message instance.

This structure was inconsistent with the rest of the package, so the object
representation for message/rfc822 content types was changed. In
email version 2, the container does return True from
is_multipart(), and
get_payload() returns a list containing a single
Message item.

Note that this is one place that backward compatibility could not be
completely maintained. However, if you’re already testing the return type of
get_payload(), you should be fine. You just need
to make sure your code doesn’t do a set_payload()
with a Message instance on a container with a content
type of message/rfc822.

The intermediate base classes
MIMENonMultipart and
MIMEMultipart have been added, and interposed
in the class hierarchy for most of the other MIME-related derived classes.

The _encoder argument to the MIMEText constructor
has been deprecated. Encoding now happens implicitly based on the
_charset argument.

The following functions in the email.Utils module have been deprecated:
dump_address_pairs(), decode(), and encode(). The following
functions have been added to the module: make_msgid(),
decode_rfc2231(), encode_rfc2231(), and decode_params().

The email package was originally prototyped as a separate library called
mimelib. Changes have been made so that method names
are more consistent, and some methods or modules have either been added or
removed. The semantics of some of the methods have also changed. For the most
part, any functionality available in mimelib is still available in the
email package, albeit often in a different way. Backward compatibility
between the mimelib package and the email package was not a
priority.

Here is a brief description of the differences between the mimelib and
the email packages, along with hints on how to port your applications.

Of course, the most visible difference between the two packages is that the
package name has been changed to email. In addition, the top-level
package has the following differences:

The method getparams() was renamed to
get_params(). Also, whereas getparams()
returned a list of strings, get_params() returns
a list of 2-tuples, effectively the key/value pairs of the parameters, split
on the '=' sign.

The Parser class has no differences in its public
interface. It does have some additional smarts to recognize
message/delivery-status type messages, which it represents as a
Message instance containing separate
Message subparts for each header block in the delivery
status notification [1].

The Generator class has no differences in its public
interface. There is a new class in the email.generator module though,
called DecodedGenerator which provides most of the
functionality previously available in the Message.getpayloadastext()
method.

The following modules and classes have been changed:

The MIMEBase class constructor arguments _major
and _minor have changed to _maintype and _subtype respectively.

The Image class/module has been renamed to MIMEImage. The _minor
argument has been renamed to _subtype.

The Text class/module has been renamed to MIMEText. The _minor
argument has been renamed to _subtype.

The MessageRFC822 class/module has been renamed to MIMEMessage. Note
that an earlier version of mimelib called this class/module RFC822,
but that clashed with the Python standard library module rfc822 on some
case-insensitive file systems.

Also, the MIMEMessage class now represents any
kind of MIME message
with main type message. It takes an optional argument _subtype
which is used to set the MIME subtype. _subtype defaults to
rfc822.

mimelib provided some utility functions in its address and
date modules. All of these functions have been moved to the
email.utils module.